NASA’s Kepler spacecraft, launched in 2009, is one of the finest and most prolific machines ever built for seeking out worlds orbiting distant stars. And at an estimated cost of $600 million, it had better be.

Now anyone can sift through a bit of Kepler’s voluminous data, obtained as the space telescope gazes at some 150,000 stars to monitor their brightness over several years. For those stars that host planets, and for those planets whose orbits are aligned with Kepler’s sight line, the spacecraft’s light sensors register a dip in the star’s brightness when a planet passes across the star’s face, a sort of partial eclipse known as a transit.

Those data are automatically filtered to locate possible planetary transits—at last count, the spacecraft had located eight exoplanets and several hundred more candidates that await confirmation. But what if the filtering algorithms miss something interesting?

Enter Planet Hunters, a citizen-scientist-powered Web site that lets any average Joe with an Internet connection peruse Kepler light curves—measurements of a star’s brightness over time—and look for the dimming signifying the possible presence of a planet. The site, which launched December 16, was created by some of the same people who produced the highly successful online galaxy-sorting project Galaxy Zoo.